Plug and socket combination having locking means in its connecting and disconnectingposition



y 1966 G. A. CORRENTI 3,263,037

PLUG AND SOCKET COMBINATION HAVING LOCKING MEANS IN ITS CONNECTING AND DISCONNECTING POSITION Filed Aug. l9, 1964 G'Mfiappg, Correm'hl 6 i JAE-W, *M Z 47'70P/VEK5 United States Patent PLUG AND SGCKET COMBINATION HAVING LOCKING MEANS IN ITS CUNNECTING AND DISCQNNECTING POSITION Giuseppe Antonio Correnti, Palermo, Italy Angelo Fontana, 411 E. 12th St., New York, N.Y.) Filed Aug. 19, 1964, Ser. No. 390,763 Ciaims. c1. ace-51.07)

The present invention relates to improvements in an electrical plug and socket combination such as commonly known wall sockets and plugs associated with electrical appliances or such as plugs and sockets which are used in electrical extension cords, etc. The invention is directed to overcoming the following dis-advantages found in conventional plug and socket combinations:

(1) The disadvantage that the plug can he accidentally pulled out of the socket or that it can slip out since in conventional plugs and sockets only frictional contact serves to hold the plug in the socket.

(2) The disadvantage that the prongs of the plug are energized While they are still partially exposed, i.e., not fully inserted into the socket, thereby making it possible for children or others to be injured by electrical shock resulting from contact with the exposed prongs.

(3) The disadvantage that the prong openings in the socket lead directly to the electrical terminals in the socket whereby a pin can be inserted into said openings by a child who would thereby receive an electric shock.

The objects of the present invention are, therefore, to overcome the above-noted disadvantages by providing a plug and socket combination wherein,

(1) The plug can be positively locked in the socket so that it cannot be accidentally pulled out or slip out; and wherein,

(2) The plug and socket function as a switch to either energize or de-energize an electrical circuit; and wherein (3) The accessible portions of the socket such as the plug-receiving opening are electrically dead while the plug is not inserted in the socket.

These and other objects are realized by providing a combination plug and socket which operates in the manher of an electrical switch, to energize or de-energize a circuit. An electrical socket is provided with a rotatable drum in which are located the slots to receive the plug prongs. The socket and the plug prongs are so constructed that, after the plug is inserted into the rotatable drum and the drum is then slightly rotated, the prongs become locked within the socket and cannot be pulled out therefrom unless the drum is first rotated back to its original position. In order to achieve electrical contact between the prongs and the socket, it is necessary to rotate the drum about 90 degrees from its initial position. With the drum in its initial or inoperative position, and with a plug inserted therein, the plug prongs make no contact with any electrical conducting elements within the socket; therefore, the plug is completely dead although it may even be fully inserted into the socket. It becomes energized only after it has been rotated about 90 degrees from the original inlet position.

A preferred embodiment of the invention is disclosed in the following detailed description in conjunction with the drawing wherein,

FIG. 1 is a front view of a socket of the present invention;

FIG. 2 is an external view of the plug in assembled condition;

FIG. 3 is a back view of FIG. 1 showing the interior of the socket while the socket is in its inoperative position;

FIG. 4 is a sectional view corresponding to FIG. 2 and showing the interior of the plug;

:FIG. 5 is a sectional view taken along line V-V of FIG. 3 and showing the plug inserted into the socket but with the plug still in its de-energized position; and

FIG. 6 is a back view corresponding to FIG. 3 but, instead, showing the socket in its energized position with the plug inserted therein.

With particular reference to FIG. 1 in the drawing, the socket A comprises the insulator case 1, -while 2 indicates a plug engaging means in the form of a rotatable drum which also is made entirely of insulating material. A metal pin 3 extends axially through the drum and serves as a ground conductor. T-shaped slots 5 are cut into the drum for receiving the plug prongs 21.

With reference to FIG. 2, the plug B comprises an insulator case 20 and prongs 21 extending therefrom. A ground contact plunger is indicated at 22.

With reference to FIG. 3, we see that the ground pin 3 has attached at its back end, a transverse ground conductor 4. Fixed .to the insulator base 1 are positive and negative electrical terminal elements 8 and 9 with suitable means 8' and 9' for attaching electrical wires thereto. A ground terminal 10 and wire connecting means 10' are also mounted within the insulator base 1. The drum 2 is rotatably mounted within the case 1. In the bottom of the case there is a cavity within which a spring 7 urges a plunger 6 upwardly. As is seen in FIG. 3, the plunger 6 engages in the lower plug slot 5 and thereby prevents the drum 2 from rotating from its inoperative position.

With reference to FIG. 5, we see that the plug B has been inserted into the socket, that is, the prongs 21 have been inserted into the recess means or slots 5. In this position one of the radial lugs or raised portions 21 of the prongs has pushed the plunger 6 against the spring 7 and out of the slot 5 thereby freeing the drum 2 for rotation within the socket case 1.

The drum 2 is provided with a circumferential slot 13 and the socket case 1 is provided with a corresponding annular shoulder or rim 14 which fits into said circumferential slot. The shoulder 14 acts as a bearing and guide for the drum 2. The shoulder 14 has openings or slots which align with the slots 5 in the drum only when it is in the disconnect position of FIG. 3. This means that only in said disconnect position, that is with the drum slots 5 aligned with the openings in the shoulder 14, will the prong elements 21' be able to move past the shoulder 14. However, after the drum 2 is rotated slightly from the position shown in FIG. 3, the prong raised portions 21' will abut against the inner side of the annular shoulder 14 and thereby prevent the plug B from being pulled out of the drum 2. It is seen in FIGURE 5 that plunger 6 moves generally transversely to the direction in which prongs 21 extend into recess 5. Of significant importance is the fact that plunger 6 is behind rim 14 (as seen in the side view of FIGURE 5). 'If plunger 6 were to the right side of rim 14, it would be a simple matter for a child, for example, to use a nail or pencil, etc., to push plunger 6 down and then rotate drum 2 to the connect position of FIGURE 6. With the arrangement of FIGURE 5, it is seen that a nail or pencil would necessarily have to extend through the slot in rim 14 in order to reach plunger 6; therefore, while said plunger may be depressed by using a nail, etc., drum 2 cannot be turned since the nail would be blocked from moving sideways by the end walls in rim 14 which define the slot through which said nail must pass.

In this particular embodiment the drum 2 is made in two separate pieces 2a and 2b separated by a spacer 20 which is of smaller diameter than either 2a or 2b and thereby provides for the circumferential slot 13. The three parts 2a, 2b, and 2c are all held together by metal pin 3 which may include a threaded end and nut. With this arrangement of parts, the socket 1 may be made in one piece and the drum 2 assembled with parts 2a and 2b on opposite sides of shoulder 14. Alternatively, drum 2 can be made in one piece and the socket 1 made in two pieces and assembled on the drum. It is, therefore, within the scope of this invention to resort to various structural modifications of the drum and of the socket case.

With reference to FIG. 6, we see the drum 2 with the plug prongs 21 therein, rotated about 90 degrees from the position of either FIGS. 3 and 5. In the position of FIG. 6, the prongs 21 respectively contact the electrical term-inal contacts 8 and 9 while the ground contact 4 contacts the ground terminal 10. In this position, the electrical connection between the plug B and the socket A is complete and electrical current can flow through these two elements.

With reference to FIG. 4, we see that the plug ground conducting device comprises the following. Element 24 is a metal piece fixed to the insulator base 29. A movable metal rod 22 is mounted on the piece 24 for axial movement thereon. The plunger rod 22 is pressed out wardly by a spring 23. When the plug B is plugged into the socket A, the external end of the rod 22 contacts the pin 3 and the spring 23 is compressed inwardly (towards the right in FIG. 4). The action of the spring 23 is to ensure that the rod 22 always has positive contact with the pin 3 when the plug is inserted in the socket while at the same time the pin 22 does not interfere with the plug being fully insertable into the socket. Electrical conducting wires are attachable to the prongs 21 and to the ground element 24 within the plug base 20.

The operation of the device is as follows:

When it is desired to connect the plug to the socket, a person simply inserts the plug prongs 21 into the drum slots 5 with lugs 21' passing through the slot means in rim 14. This accomplishes the first function of disengaging the plunger 6 from within the lower slot 5. This is called the disconnect position. Then the person simply twists the plug B through an angle of about 90 degrees and this accomplishes the remaining two functions. Primarily, after a very slight twist of the plug B, the plug is locked within the socket A by virtue of the prong lugs 21 abutting against the annular shoulder 14, and secondly, after the plug B has been turned about 90 degrees, the prongs 21 respectively contact the fixed contact elements 8 and 9, and the movable transverse ground conductor 4 contacts the fixed ground terminal 16. This is called the connect position.

When it is later desired to electrically disconnect the plug from the socket without physically removing the plug from the socket, it is only necessary to twist the plug B back about 45 degrees, this causing the prongs 21 to lose contact with the contacts 8 and 9 while, however, the prong lugs 21 are still opposed and abutted by the annular shoulder 14. Still later, if it is desired to reconnect the plug electrically, it is merely necessary to twist it back to its 90 degree position, while, on the other hand, if it is desired to physically remove the plug from the socket, the plug is twisted to the position of FIGS. 3 and 5 and simply pulled out of the socket. Appropriate stops, not shown in the drawing, are provided at the respective positions of FIGS. 3 and 6 in order to assure that the plug is not twisted past those two extreme positions.

From the above, it is seen that the plug and socket actually function as an electrical switch to either energize or de-energize a circuit, while also being completely disengagable from each other.

An appropriate insulating cover, not shown in the drawing, can be provided to cover the back of the socket which appears in FIGS. 3 and 6.

Various modifications in the preferred embodiment are within the scope of this invention, e. g., the plug B is not limited as to the number of prongs 21 that it may have. The plug may have one or more prongs, depending on the electrical character of the device being served by the plug.

Also, the degree of rotation from the position of FIG. 3 to that of FIG. 6 may vary from the degrees of the preferred embodiment depending on the number of prongs and on the particular choice of the manufacturer. The prongs 21 and their raised portions 21 may conform to any convenient shape, the important consideration being that the prongs initially push the plunger 6 out of the 'way and that they be able to lockingly engage behind the annular shoulder 14. Further, it is not essential that the prongs themselves comprise the locking lugs 21'. For example, the lugs 21' could be eliminated and the plug locking feature could be incorporated into the plug base 20 which could include a tooth which would lockingly engage with a slot in the socket base 1. It is of course understood that the shape of slots 5 will vary to depend upon the shape of the prongs 21. The particular ground conducting means 22, 24, 3 and 4 could also be modified within the inventive concept of this invention.

The drum locking means 6 and 7 can also be modified; for example, the coil spring 7 and plunger 6 could be replaced by a leaf spring bearing against a recess in drum 2. Also, other than spring means could be used to lockingly press against the drum; for example, a plunger such as 6 could be located in the top portion of the case 1 and it could bear against the drum by virtue of either its own weight or under force of a separate weight.

The drum 2 itself need not be round. A square or triangular shaped drum, for example, could be used which would be appropriately mounted for rotation within the socket base 1. Further, the drum 2 could be mounted with-in the socket base 1 by means other than the groove 13 and rim 14. For example, the drum 2 could be mounted between front and back annular rims on the base 1 with the base 1 being made in two pieces, front and back, assembled about the drum. Corresponding plug locking means could then be provided.

It is to be understood, therefore, that various modifications are within the scope of this invention whose scope is only limited by the following claims.

What is claimed is:

1. A switch-type electrical plug and socket combination comprising a plug and socket, said socket comprising an insulator base and electrical terminal means mounted therein, a drum made of electrically insulating material rotatably mounted in said base, said drum comprising recess means, said plug comprising an insulator base and electrical prong means mounted in said plug base and extending therefrom, said prong means being insertable into said drum recess means, said drum being rotatable with said plug prong means located in said recess means between disconnect and connect positions, in said disconnect position said prong means being out of contact with said base terminal means, and in said connect position said prong means being in contact with said base terminal means, drum lock means to lock said drum in said disconnect position and to unlock said drum pursuant to insertion of said plug into said drum recess means, said lock means being actuable to unlock said drum when said plug prong means is inserted into said drum recess means, and plug lock means to prevent withdrawal of said plug prong means from said drum recess means when said drum is in a rotative position other than said disconnect position.

2. The combination of claim 1, wherein said drum lock means comprises an element biased into said drum recess means, said prong means pushing said element out of said recess means when said prong means are inserted into said recess means thereby releasing said drum from locking engagement with said lock means, said prong means being fully receivable in said recess means with said drum being in its disconnect position.

6. The combination of claim 1, wherein said drum comprises a circumferential groove and said socket base comprises an annular rim extending into said groove, said rim comprising slot means which are in radial alignment with said recess means when said drum is in said disconnect position, said prong means comprising radially extending lug means, said prong means being insertable into said drum recess means with said lug means passing through said slot means when said drum is in said disconnect position, said lug means abutting a radial face of said rim when said drum is in a rotative position other than said disconnect position, said drum lock means comprising an element movable into and out of said drum recess means, said element being movably mounted in said socket base axially behind said rim and in alignment with a one of said rim slot means.

4. A switch-type electrical plug and socket combination comprising a plug and socket, said socket comprising an insulator base and electrical terminal means mounted therein, a drum made of electrically insulating material rotatably mounted in said base, said drum comprising recess means, said plug comprising an insulator base and electrical prong means mounted in said plug base and extending therefrom, said prong means being insertable into said drum recess means, said drum being rotatable with said plug prong means located in said recess means between disconnect and connect positions, in said disconnect position said prong means being out of contact with said base terminal means, and in said connect position said prong means being in contact with said base terminal means, a metallic pin extending axially from one end to the other end of said drum, said socket terminal means comprising a .ground terminal mounted in said socket base, means on one end of said metallic pin being electrically connectable with and disconnectable from said ground terminal in correspondence to said drum being respectively in said connect and disconnect positions, said plug comprising a ground element contacting the opposite end of said metallic pin when said plug prongs are inserted into said drum.

5. The combination of claim 4, wherein said plug ground element comprises a ground plunger mounted in said plug base and elastically biased to protrude from said plug base, said ground plunger being elastically pressed into contact with said opposite end of said metallic pin when said plug prongs are inserted into said drum.

6. The combination of claim 2, wherein said socket base comprises a cavity extending radially from said drum and in alignment with said drum recess means when said drum is in said disconnect position, said biased element comprising a plunger movably mounted within said cavity and a resilient means within said cavity and urging said plunger into said drum recess means, said plunger being movable into and out of said drum recess means along a direction which is transverse to that in which said plug prongs are insertable into said drum recess means.

7. An electrical plug and socket combination comprising a plug and socket, said socket having electrical terrninals mounted therein and said plug comprising corresponding contact means selectively engageable with said socket terminals, a plug engaging means mounted in said socket, plug lock means adapted to lock said plug relative to said engaging means, said engaging means being displaceable relative to said socket between disconnect and connect positions, in said disconnect position said engaging means and said plug contact means being out of contact relative to said socket terminals and said engaging means covering said terminals relative to the exterior of said socket, and in said connect position said plug contact means being in electrical contact with the corresponding socket terminals, said combination including a releasable second lock means to lock said engaging means in said disconnect position.

8. The combination of claim -7, wherein said plug contact means comprises prong means and said plug engaging means comprises recess means adapted to receive said prong means therein, said plug lock means comprising corresponding abutment means on said prong means and on said socket, said abutment means being engageable with each other in correspondence to said engaging means being displaced from said disconnect position, said second lock means comprising a member mounted in said socket and resiliently urged into said recess means and thereby preventing displacement of said engaging means from said disconnect position, said prong means displacing said member out of said recess means in correspondence to said prong means being received within said recess means.

9. The combination of claim 8, wherein said socket abutment means includes a slot means aligned with said recess means in said disconnect position of said plug engaging means and wherein said prong means are insertable into said recess means and through said slot means in said disconnect position and wherein said second lock means member is, in frontal view, aligned with said recess and slot means in said disconnect position of said engaging means, and said lock means member is, in side View, behind said socket abutment means whereby said second lock means member is displaceable upon said prong means extending at least past said socket abutment means into said recess means.

it). The combination of claim 11, wherein said plug lock means is actuable to lock said plug relative to said socket wit-h said drum being in said disconnect position.

References Cited by the Examiner UNITED STATES PATENTS 1,618,939 2/1927 Marth 339189 2,484,558 10/1949 Eisner 174-51 2,926,327 2/11960 Metelli 339-41 3,112,973 12/1963 Von Holtz 339189 FOREIGN PATENTS 614,286 12/ 1960 iItaly.

ROBERT K. SCHAEFER, Primary Examiner.

KATHLEEN H. CLAF'FY, Examiner.

B. SMITH, JR., Assistant Examiner. 

1. A SWITCH-TYPE ELECTRICAL PLUG AND SOCKET COMBINATION COMPRISING A PLUG AND SOCKET, SAID SOCKET COMRPISING AN INSULATOR BASE AND ELECTRICAL TERMINAL MEANS MOUNTED THEREIN, A DRUM MADE OF ELECTRICALLY INSULATING MATERIAL ROTATABLY MOUNTED IN SAID BASE, SAID DRUM COMPRISING RECESS MEANS, SAID PLUG COMPRISING AN INSULATOR BASE AND ELECTRICAL PRONG MEANS MOUNTED IN SAID PLUG BASE AND EXTENDING THEREFROM, SAID PRONG MEANS BEING INSERTABLE INTO SAID DRUM RECESS MEANS SAID DRUM BEING ROTATABLE WITH SAID PLUG PRONG MEANS LOCATED IN SAID RECESS MEANS BETWEEN DISCONNECT AND CONNECT POSITIONS, IN SAID DISCONNECT POSITION SAID PRONG MEANS BEING OUT OF CONTACT WITH SAID BASE TERMINAL MEANS, AND IN SAID CONNECT POSITION SAID PRONG MEANS BEING IN CONTACT WITH SAID BASE TERMINAL MEANS, DRUM LOCK MEANS TO LOCK SAID DRUM IN SAID DISCONNECT POSITION AND TO UNLOCK SAID DRUM PURSUANT TO INSERTION OF SAID PLUG INTO SAID DRUM RECESS MEANS, SAID LOCK MEANS BEING ACTUATABLE TO UNLOCK SAID DRUM WHEN SAID PLUG PRONG MEANS IS INSERTED INTO SAID DRUM RECESS MEANS, AND PLUG LOCK MEANS TO PREVENT WITHDRAWAL OF SAID PLUG PRONG MEANS FROM SAID DRUM RECESS MEANS WHEN SAID DRUM IS IN A ROTATIVE POSITION OTHER THAN SAID DISCONNECT POSITION. 